Aperture: Avoid making manual changes to your library structure

Aperture's library is not designed to be manipulated manually from the Finder.

Manually altering the contents of the Aperture library in the Finder is not recommended. In Aperture 2.x and later it is especially important to avoid manual changes within the Aperture Library. Make all changes to your library from within Aperture, whenever possible. If you experience issues with your Aperture library, restore it from a recent backup if one is available, or use the Aperture Library First-Aid tools by holding down the Command and Option keys when starting Aperture.